Still no time to write anything substantial. Here are some yellow flowers, now (or recently) blooming in the Maryland piedmont.
a yellow haze of spicebush flowers (Lindera benzoin; Lauraceae)
another flowering shrub, leatherwood (Dirca palustris; Thymelaeaceae), S2/threatened in Maryland
trout lilies (Erythronium americanum; Liliaceae) will be blooming for another week or so in the Potomac gorge
Corydalis flavula (short-spurred corydalis or yellow fumewort; Papaveraceae)
one very early sessile bellwort (Uvularia sessilifolia; Liliaceae); watch for more in the next week or so in the gorge, maybe a week after that further north and west in the piedmont
masses of golden ragwort (Packera aurea; Asteraceae) are blooming now along the Potomac; watch for them on the eastern part of Billy Goat C
smooth yellow violet, aka yellow forest violet (Viola pubescens var. scabriuscula; Violaceae)
Elizabeth's Wildflower Blog 
You certainly have some odd ones on the far side of the continent. Only the violet in the last picture looks familiar, sort of like a flatter version up in Western Oregon.
Ms. Miller, thank you for such a beautiful and well written blog, which I found while searching for photos of Thalictrum coriaceum. I am writing profiles of rare plant species for the Georgia Dept of Natural Resources’s rare plant website. I’d love to incorporate some of your photos of Thalictrum coriaceum into the profile for that species. If you are willing, please email me at LCHAFIN@UGA.EDU and I can give you more information about the project. Thanks so much, Linda Chafin, Conservation Botanist, State Botanical Garden of Georgia.